It is known that TXA.sub.2 is a powerful platelet aggregating agent and also a strong vasoconstrictor as described in Shozo Yamamoto (ed.), Arachidonate Cascade and Drugs, Gendai Iryosha (1985). TXA.sub.2 also acts as a strong constrictor of the bronchi and tracheal smooth muscle. TXA.sub.2 is thus considered to be involved in a broad range of diseases as enumerated below.
(1) Ishaemic diseases, e.g., myocardial infarction, angina pectoris, and thrombosis
(2) Cerebral vascular diseases, e.g., temporary ischemia, migraine, apoplectic stroke, and infarct
(3) Peripheral vascular diseases and diseases caused by lipid imbalance, e.g., atherosclerosis, capillary vasospasm, peripheral circulatory insufficiency, hypertension, and pulmonary embolism
(4) Inflammatory and allergic diseases, e.g., bronchial asthma, bronchitis, pneumonia, naphritis, and hepatitis
(5) Shocks, and
(6) Metastasis of cancers
It is therefore expected that a compound inhibiting TXA.sub.2 synthase would have therapeutic effects in the treatment or prevention of one or more of the above-described diseases or any other diseases on which inhibition of TXA.sub.2 synthase exerts a favorable influence. Further, when combined with conventional medicines whose usefulness has been limited due to appearance of side effects involving or probably involving TXA.sub.2, such a compound is expected to reduce the side effects.
Typical examples of the conventinal inhibitors of TXA.sub.2 biosynthesis are recited in Yuki Gosei Kagaku Kyokaishi, Vol. 45, p. 2 (1987). Further included in the TXA.sub.2 biosynthesis inhibitors are imidazole derivatives of formula: ##STR2## as disclosed in JP-A No. 61-18770 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") corresponding to U.S. Pat. Nos. 4,665,188 and 4,777,257 and pyridine derivatives of formula: ##STR3## as disclosed in JP-A No. 60-100555 corresponding to U.S. Pat. No. 4,563,446 both of which carry a carboxyl group at the terminal.
Tricyclic pyridine derivatives relevant to the compounds according to the present invention include benzocycloheptapyridine derivatives having formula (II) hereinafter described wherein X.sup.1 --X.sup.2 is --CH.dbd.CH-- or --CH.sub.2 CH.sub.2 --, and those wherein the oxo (.dbd.O) is replaced by an imino group (.dbd.NR) or an amino group (--NHR) as described in J. Heterocyclic Chem., Vol. 19, p.897 (1982) and ibid, Vol. 19, p.967 (1982); and benzocycloheptapyridine derivatives of formula (II) wherein X.sup.1 --X.sup.2 is ##STR4## and the oxo is replaced by a methyl group and a hydroxy group or an acetamido group as described in J. Heterocyclic Chem., Vol. 23, p. 961 (1986).